newell.] TUOLUMNE RIVER, CALIFORNIA. 83 
MODESTO STATION, ON TUOLUMNE RIVER. 
Observations of river height at the railroad bridge crossing Tuolumne 
River, 1 mile south of Modesto, have been kept by the Southern Pacific 
Railroad Company for a number of years. On November 12, 1889, 
William P. Trowbridge, jr., hydrographer of the Irrigation Survey, 
under instructions from William Ham. Hall, supervising engineer, 
began a series of measurements at this point, both for the purpose of 
determining the flow of the stream and for experimentally ascertain- 
ing the best methods and apparatus for making velocity measurements 
upon rivers of this class. In this work he was delayed by the unfa- 
vorable weather then prevailing, rain continuing from November 17 to 
January 1, 1890, with hardly a break, much of the time being accom- 
panied by violent winds. The first work was to place in position a 
permanent gage, this being attached to the central pier of the railroad 
bridge. Under orders from William Hood, chief engineer of the South- 
ern Pacific Company, the railroad employees furnished a well-painted 
gage and secured it in position, under Mr. Trowbridge's supervision. 
The bridge tender, G. G. Nelson, was also instructed to furnish daily 
readings of the height of water, copies of his observations being sent 
to the railroad office and to Mr. Hall. 
A one-half-inch cable was stretched across the river at a point about 
200 feet above the bridge, this being a distance sufficiently great to be 
removed from the influence of the bridge piers. At this point the stream 
is about 220 feet wide, and has an average depth of from 5 to 7 feet at 
ordinary stages, and from this up to 20 feet in times of flood. A small 
topographic map was then made of the vicinity, by means of transit 
and stadia, and cross sections were run at various distances above and 
below the station in order to furnish data for the study of the stream 
bed in that vicinity. Longitudinal sections were also run, and bench 
marks placed at intervals of 500 feet for a distance of 1,000 feet above 
and below the section. Small temporary gages were placed at the 
extreme ends of this line for the purpose of obtaining the slope of 
the river at its various stages, by means of simultaneous gage read- 
ings. All bench marks were referred to the plane of the zero mark of 
the gage on the bridge, this being the reference plane for all work at 
this locality. This zero mark was referred to the railroad track. 
A light, safe catamaran was constructed, capable of being taken 
apart and shipped to any point, and from this velocity measurements 
were made. It was determined, however, that the method of obtaining 
velocity measurements from shore, or the cable and traveling apparatus, 
should be tried experimentally. This, as devised by Mr. Hall and put 
into operation by Mr. Trowbridge, consists of two cables stretched 
across the stream; from one of these — the lower — the meter is sus- 
pended by suitable cords and pulleys, and held from being swept down- 
stream by a stay line which runs to the upper cable. A brief descrip- 
